Orthoses are often considered to be devices, external of the body, that serve to or are used to alter, modify, or support, structural and/or functional characteristics of the body's skeletal or neuromuscular systems. For example, an orthosis may be used to retard the progression of scoliosis or may be used to assist a person, such as a person suffering with foot nerve damage, with walking. Orthoses can provide confinement and support in static situations, such as in retarding further spinal curving of a patient with scoliosis, and in dynamic situations, such as with supporting and influencing gait of a patient suffering from drop foot. An orthosis may also immobilize, limit, steer, guide, or dictate the position or range of movement of a body extremity, a body joint, or a body area. Orthoses may be used for treatment, improved lifestyle, improved comfort, and for other reasons as well.
In certain orthoses, the weight of the wearer's body may be transferred through the orthosis; and certain orthoses may be used for restorative effects during rehabilitation. Ankle Foot Orthoses (AFOs), including the subset of Knee Ankle Foot Orthoses (KAFOs), are examples of orthoses whose names identify the body parts that they are designed to supplement, restrict, guide, support or otherwise assist.
An orthotist may classify an orthosis as being a static orthosis or a functional orthosis. For example, a static orthosis may be used to stabilize a joint and surrounding soft tissue after surgery, hence it is used as an immobilization device. A functional orthosis, on the other hand, can be used to guide a joint to regain or maintain the normal joint function and/or to support a joint and/or surrounding soft tissue to ameliorate neuromuscular weakness. Orthoses used to guide or support a user through an activity or movement, such as normal gait, can be equipped with external joints, often called articulated orthoses, such as articulated Ankle Foot Orthoses.